Without limiting the scope of the invention, its background is described in connection with single-wafer rapid thermal processing of semiconductors wafers, as an example.
Single-wafer rapid thermal processing (RTP) of semiconductors is a powerful and versatile technique for fabrication of very-large-scale-integrated (VLSI) and ultra-large-scale-integrated (ULSI) electronic devices. It combines low thermal mass photon-assisted rapid wafer heating with inert or reactive ambient semiconductor wafer processing. Both the wafer temperature and the process environment can be quickly changed and, as a result, each fabrication step can be independently optimized in order to improve the overall electrical performance of the fabricated devices.
Rapid thermal processing (RTP) of semiconductor wafers provides a capability for improved wafer-to-wafer process repeatability in a single-wafer lamp-heated thermal processing reactor. In prior art RTP systems, equipment manufacturers have spent significant design resources to provide uniform wafer heating during the steady-state heating, conditions. These prior art systems are designed with illuminators which provide single-zone or very limited asymmetrical multi-zone control capability. Thus, with an increase or decrease of power to the illuminator, the entire wafer temperature distribution is affected. As a result, there are insufficient real-time adjustment and control capabilities to adjust or optimize wafer temperature uniformity during the steady-state and dynamic transient heat-up and cool-down cycles. As a result, the transient heat-up or cool-down process segments can produce slip dislocations as well as process non-uniformities. Various process parameters can influence and degrade the RTP uniformity. Prior art RTP systems are optimized to provide steady-state temperature uniformity at a fixed pressure. Thus a change in pressure or gas flow rates may also degrade the RTP uniformity.